Quality of the TV and the tech that's on it makes difference. I have an oled with HDR , Vision etc. And for me 4k blu rays are a noticeable improvement ,but I won't be replacing any standard blu rays I already own.

The 4k blu ray player can make a difference here too , I think most people are going for the midland high tier Panasonic players these days

Audio is a big step up on alot of the 4k discs also so give some consideration to your sound setup also.

There are a few novels based on aliens and one of them has a secret lab on earth they are experimenting with them and guess what inevitably happens !